1. Technical Field
The invention relates to teleconferencing. In particular, the invention relates to methods and systems that permit the appearance of eye-contact to be maintained between participants in a teleconference
2. Description of the Prior Art
A primary concern with video teleconferencing systems is the frequent lack of eye-contact between participants. In the most common configuration, each participant uses a computer monitor on which an image of the remote participant is displayed, while a camera mounted above the monitor captures an image of the local participant for display on the monitor of the remote participant. Because participants frequently look at either at the image of the remote participant or elsewhere on the display, rather than directly at the video camera, there is the appearance that the participants are not looking at one another. This results in an unsatisfactory user experience.
Prior art solutions to the eye-contact problem have incorporated half-silvered, partially transmissive and partially reflective mirrors, or beamsplitters. These solutions have typically incorporated a beamsplitter placed in front of a computer display at a 45 degree angle. In one typical configuration, a video camera, located behind the beamsplitter, captures the image of the local participant through the beamsplitter. The local participant views an image of the remote participant on the display as reflected by the beamsplitter.
In devices incorporating a conventional CRT, the resulting device is both bulky and physically cumbersome. In cases involving an upward facing display, the display is viewable both directly and as reflected by the beamsplitter, greatly distracting the local participant. To alleviate this problem, prior solutions, including those described in U.S. Pat. Nos. 5,117,285 and 5,612,734 have introduced complicated systems involving polarizers or micro-louvers to obstruct a direct view of the upward facing display by the local participant. In all cases, the image of the remote participant appears recessed within the housing holding the display, beamsplitter, and video camera. The resulting distant appearance of the remote participant greatly diminishes the sense of intimacy sought during videoconferencing.
Another set of prior art attempts seeks to alleviate this problem through the use of computational algorithms that manipulate the transmitted or received video image. For example, U.S. Pat. No. 5,500,671 describes a system that addresses the eye-contact problem by creating an intermediate three-dimensional model of the participant based on images captured by two video cameras on either side of the local display. Using this model, the system repositions artificially generated eyes at an appropriate position within the image of the local participant transmitted to the remote participant. The resulting image, with artificially generated eyes and a slight but frequent mismatch between the position of the eyes relative to the head and body of the participant, is unnatural in appearance. Furthermore, the creation of an intermediate three-dimensional model is complex and time-consuming, making it difficult to implement in practice.
A further weakness of these and other similar approaches is an inability to handle all possible participant postures and movements. More robust algorithms are possible and several have been proposed, but these approaches are more computationally complex, and cannot be executed rapidly enough on current microprocessors to allow for real time processing of high resolution video images. Finally, many of these approaches require that the remote communicant own and operate the same videoconferencing device. This presents a significant obstacle to introduction and widespread adoption of the device.
What is needed is a device that incorporates at once all of the beneficial features achieved by the prior art, while addressing the aforementioned deficiencies. First and foremost, the device must offer eye-contact in a robust manner, operating effectively across the full range of local participant head positions and gaze directions. It must provide a natural view of the remote participant for the local participant. It must be aesthetically pleasing and easily operated by a typical user. The underlying algorithm must be computationally simple enough to be conducted in real time on high frame rate, high resolution video. Finally, the device should require little if any additional videoconferencing equipment beyond that found in a typical existing videoconferencing setup.
The invention comprises a structured light projector, a video camera, and an image processor, for achieving perspective corrected images that enhance eye-contact during teleconferencing. A structured light projector is offset in one direction from the monitor center, and illuminates a local participant with a structured light pattern. The image of the local participant, illuminated by both ambient and structured light, is captured by the video camera, also offset from the monitor center, preferably in the direction opposite the structured light projector. By considering the distortion of the structured light observed from the position of the video camera and the position of the structured light projector and video camera relative to the monitor center, an image processor creates an image of the local participant as viewed from a perspective that, when viewed by the remote participant, provides a sense of eye contact with the local participant.